Power converters such as power adapters or chargers become indispensable electronic devices for many kinds of electrical apparatuses. For example, by means of the power adapters, the utility power may be rectified and then converted into DC power for supplying power-receiving devices such as notebook computers. Alternatively, by means of the chargers, the converted DC power may be charged into the rechargeable batteries of the power-receiving devices such as mobile phones or digital cameras.
A power converter principally includes a casing, a plug and a circuit board mounted within the casing. Via the plug, external power is transmitted to the circuit board. The arrangement of the circuit board is dependent on the function of the power converter, for example being as an adapter or a charger, to perform rectification or conversion for a power-receiving device.
Referring to FIG. 1, a schematic perspective view of a conventional power adapter is illustrated. The power adapter 10 of FIG. 1 includes a casing 11, a plug 12 and a circuit board (not shown) mounted within the casing 11. Conventionally, the plug 12 of a power adapter is composed of two conducting pins, which are projected from one side of the casing 11. In a case that the power adapter is not in use, a user is easily hurt by the tips of projected pins or the projected pins are readily bent or broken due to a sudden impact. In addition, the plug 12 is difficultly stored when the power adapter is not used.
Recently, a power converter having a foldable plug has been developed in order to solve the above problems. Please refer to FIGS. 2A and 2B, which are respectively perspective and cross-sectional views illustrating a power converter having a foldable plug. The power converter 20 of FIGS. 2A and 2B includes a casing 21 and a plug 22. The casing 21 further has a concave portion 23 near the top edge of the casing 21. The plug 22 principally includes a rod 220, two first pins 221 and two second pins 222. Both ends of the rod 220 are formed as tenons 2201. The first pins 221 and the second pins 222 respectively have holes 223 and 224 corresponding to the tenons 2201. The tenons 2201 are inserted into the holes 223 and 224 such that the first pins 221 and the second pins 222 are fixed onto the rod 220. Each sidewall of the concave portion 23 has a spring receptacle 226 containing a spring 227 therein. An end of the spring 227 is in contact with a side of the spring receptacle 226 and the other end of the spring 227 is coupled with a sustaining element 228. The sustaining element 228 is embedded into an indentation 225 of the first pin 221. As a consequence, the plug 22 is positioned in the concave portion 23 by the resilience force of the springs 227. By rotating the first pins 221 with respect to the rod 220, the second pins 222 are rotated to be contacted with contact points of the circuit board. Meanwhile, the plug 22 may be inserted into a power socket (not shown) to receive external power.
Although the above-mentioned power converter has a foldable plug, there are still some drawbacks. For example, the configuration of the foldable plug and the process for assembling such a foldable plug are complicated. In addition, the plug is usually not securely positioned on the casing because the pins are easily detached from the tenons.
In views of the above-described disadvantages resulted from the conventional method, the applicant keeps on carving unflaggingly to develop an electronic device having a foldable plug according to the present invention through wholehearted experience and research.